shortcut for running the simulation in Blender 2.8 instead of Alt+A?
The shortcut is SPACEBAR to play the animation, if you're using the default Blender 2.8 or Industry Compatible keymap. In case you have mapped Tools or Search to SPACEBAR, then it's SHIFT+SPACEBAR.

You can check what is mapped to your spacebar in the preferences (Edit > Preferences > Keymap).